Solid electrolytic capacitors use for their anodes a metal that can form an electrically insulating oxide film thereon, such as aluminum, titanium, brass, nickel, or tantalum, i.e., so-called valve metal. On the surface of the valve metal, the insulating oxide film is provided by anodizing the surface. Thereafter, a solid electrolyte layer substantially functioning as a cathode is formed on the oxide film. The solid electrolyte layer is made of a material such as an organic compound. Also, an electrically conductive layer made of a material such as graphite or silver is provided as a cathode on the solid electrolyte layer. The solid electrolytic capacitor is manufactured through these processes.
In order to reduce the impedance of the solid electrolytic capacitor, it is necessary to lower ESL (equivalent series inductance) and ESR (equivalent series resistance). In particular, for achieving high-frequency operations, it is necessary to keep the ESL low. In general, the following methods for lowering the ESL are known: first, setting the length of a current path as short as possible, second, canceling out a magnetic field formed by a current path by that formed by another current path, and third, dividing a current path into N paths so that the effective ESL becomes 1/N. For example, the invention disclosed in Japanese Patent Application Laid-Open No. 2000-311832 employs the first and third methods. The invention disclosed in Japanese Patent Application Laid-Open No. HEI 06-267802 employs the second and third methods. The inventions disclosed in Japanese Patent Applications Laid-Open Nos. HEI 06-267801 and HEI 11-288846 employ the third method.